The present invention relates to dental handpiece assemblies having one sleeve which is to be detachably mounted in locked position to a second sleeve to allow driving force to be transmitted through the sleeves to drive a dental tool in the head of the handpiece. In the prior art there have been handpieces having means to hold one sleeve portion of a handpiece to another sleeve portion of a dental handpiece. However, those devices have not provided the ease in attachment and detachment and operational advantages provided by the present invention.
The present invention has a handle sleeve having a notch. A lock ring having a slot is rotatably mounted to a mounting sleeve projecting from the handle. A spring is mounted to the handle and to the locking ring, and biases the ring towards the notch so that it partially blocks the handle notch.
A shoulder sleeve has a locking extension with a lug on its end. The shoulder can be mounted to the locking ring so that the extension passes through the ring slot to allow the lug to come against the edge of the handle notch. The end surface of the lug is shaped so that when the lug is pushed towards the handle notch, the lug surface presses against the notch edge to guide the lug into the notch. As the lug is guided into the notch it also moves the lock ring to allow the lug to pass through the lock ring slot into the notch. After the lug enters the notch, the ring is rotated by the spring to block passage of the lug out of the notch, so that the lug can be locked without having to rotate the ring with the fingers.
In the preferred embodiment of the invention, the notch and slot are on the surfaces of the handle and ring respectively, so the operator can easily view the lug and ring to see if the lug is in the locked position. The operator can also lock the shoulder sleeve to the handle sleeve without looking at the two pieces, as by using his or her fingers to ascertain the location of the locking extension and the ring slot, the pieces can be moved to be locked. In the preferred embodiment, the spring is helical and is positioned against exposure by being hidden within the ring. The spiral spring provides biasing action, while allowing deformation of spring length to be only a small fraction of the overall spring length. In the preferred embodiment, the spiral spring is mounted at one end to a pin extending from the handle and at the other end to a pin extending from the lock ring, and the ring has an aperture which receives the handle pin to prevent overextension of the spring. The preferred embodiment features the surface of the ring being approximately flush with the surfaces of its adjacent shoulder and handle sleeves so that it does not protrude, to thus prevent accidental operation. A bearing for a rod connecting drive gears is used to hold the lock ring to the handle.